This invention relates to an improved carpet underlay which provides a comfortable feeling to the person walking on the carpet placed thereover while eliminating the need for using hot melt seams during the carpet installation.
In a commonly used method of installing carpet the carpet is installed over a tackless strip secured to the floor around the walls of a room, the strip being provided with a series of upwardly protruding nails or tacks. The carpet is hooked onto the protruding nails of the strip on one side of the room and is then stretched before it is hooked up to the nails on the strip on the opposite side of the room. Since the carpet, and any padding which may be beneath it have a tendency to wrinkle after the carpet has been subjected to traffic, it is necessary to pull up the carpet, stretch it, trim it and fasten it again to the tackless strip. Installation of tackless strip is time-consuming and presents a problem if the floor is not a wooden floor to which the strip can be easily secured.
In order to avoid restretching of the carpet and even the padding or underlay, many installers have merely directly glued the carpet to the floor without using a carpet underlay. However, in the absence of padding, one walking on such an installed carpet does not have the same cushiony feeling imparted to him as is imparted when he walks on a carpet installed over a padding or carpet underlay. The carpet, instead, feels hard and unyielding under foot.
In an effort to improve the comfort of walking on the carpet surface, it has been suggested to glue a conventional carpet cushion or underlay directly to the floor. While this method has met with some success, it also suffers significant drawbacks. When applying the adhesive to the floor via a spray application, the overspray mist coats the wall, ceilings, curtains, etc. in the room being carpeted. In addition, the carpet cushion tends to absorb the adhesive and when the cushion is pulled away from the floor after it has been in place for a period of time, it delaminates with portions of the underlay tearing off and remaining adhered to the floor. As the carpet is subjected to traffic, the cushion has a tendency to become substantially permanently compressed because of the absorbed adhesive, and most of its cushioning capability is lost. This failure of the cushion to rebound is called memory failure.
U.S. Pat. No. 4,647,484 discloses a carpet underlay which is laid without the use of an adhesive between the floor and cushion. A double-faced tape formed of a Mylar polyethylene terephthalate film coated on each side with a pressure sensitive adhesive is secured to the upper surface of the cushion, which cushion consists of a rubber material formed onto a glass scrim. A release film is removed to expose the pressure sensitive adhesive onto which the carpet is then laid and secured by the adhesive.
The use of a pressure sensitive adhesive creates a relatively weak bond between the carpet and the cushion and such bond is not sufficiently strong to maintain a seam between two adjacent pieces of carpet laid over the underlay. To firmly join two carpet pieces in adjacent edge to edge relationship, a hot melt seam is usually utilized. While hot melt seams provide a strong carpet joint along adjacent carpet edges, their major drawback is that a visible line is evident along the seam. Additionally, the hot melt seam can usually be felt as one walks across the carpet seam. If a hot melt seam is not used to join the adjacent pieces of carpet, the carpet will tend to lift up at the joint or seam because the pressure sensitive adhesive bond is not sufficiently strong to firmly maintain the carpet in sealed relationship on the surface of the underlay.
Alternatively, the carpet cushion may be stapled or nailed to the floor, but this creates noticeable dimples in the surface of the cushion and if the carpet is made t adhere to the cushion, the recesses in the cushion caused by the nail or staple can be noticeable to the person walking on the carpet. Furthermore, the nails and staples may be uncomfortable when one steps on the carpet directly over them.
U.S. Pat. No. 4,557,774 describes a carpet cushion having a sealant disposed on both surfaces and a scrim webbing having pressure sensitive adhesive on both sides is adhered to each of the sealed cushion surfaces for securing the undersurface of the carpet cushion to the floor and for securing the carpet to the upper surface of the cushion. The pressure sensitive adhesive is non-permanent, so as to always allow for temporary lifting of the carpet wholly or in localized areas when desired.
The pressure sensitive adhesive based system disclosed in this U.S. Pat. No. 4,557,774, suffers from the same drawbacks with regard to carpet seams as discussed above. The patentee does disclose that if the carpet cushion is adhered to the floor by stapling or tacking, the dimples formed in the cushion will not be noticeable to the viewer of the carpet, provided that the carpet is not adhered to the carpet cushion in the areas of stapling or tacking.